1. Field of the Invention
The present invention relates to image processing apparatases and image forming apparatuses.
2. Description of the Related Art
An image processing apparatus divides image data into bands of which each one includes a predetermined number of lines, compresses the plural bands, and keeps the compressed plural bands in a memory or the like.
Further, another image processing apparatus identifies plural sub-bands by dividing a band in the primary scanning direction, compresses each of the sub-bands, and keeps the plural compressed sub-bands as the image data.
In order to perform image processing for the kept image data, an image processing apparatus decompresses plural pieces of sub-band data (i.e. image data of plural sub-bands) of one band to restore image data of the one band, and performs the image processing for the image data of the one band.
For such a process, a decompression processing module decompresses pieces of sub-band data to restore image data of the one band, and an image processing module performs the image processing band by band for the image data of the one band; and a work memory is disposed between them and transfers the image data from the decompression processing module to the image processing module in order to enable the both processing modules to run in parallel. The work memory includes one or more buffers, and each of the buffers has a size sufficient to store image data of one band.
In a case that the orientation of an image is “portrait”, the length (i.e. number of pixels) of the image in the primary scanning direction is smaller than the length of the image in the secondary scanning direction. Contrary to this, in a case that the orientation of an image is “landscape”, the length of the image in the primary scanning direction is larger than the length of the image in the secondary scanning direction. Thus, the size of image data of one band in a case that the orientation of the image is “landscape” is larger than that in a case that the orientation of the image is “portrait”.
Therefore, in general, the aforementioned work memory includes the buffer of which the size is sufficient to store image data of one band in the image of which the orientation is “landscape”.
As mentioned, the size of a work buffer between processing modules is set in correspondence to image data of one band in an image of which the orientation is “landscape”, and consequently, the large size of the work buffer are required.